Field of the Invention
The present invention relates to a control method for hill start assistant control system, and more particularly to a control method of operating a hill stat assistant control system without an error in a pitching motion of a vehicle due to sudden stop by normally recognizing a hill even when the vehicle starts after sudden stopping.
Description of Related Art
A driver takes a foot off the brake pedal and presses down the acceleration pedal to start a vehicle stopped on a hill (uphill road), in which the vehicle may be pushed down the hill due to the deficit of driving force.
Accordingly, a hill start assistant control system (hereafter, referred to as a ‘HAC’) that prevents a vehicle from being pushed back by sensing that the vehicle is pushed back with wheel speed sensors on the wheels and by generating a braking force on the wheels with a brake system when the vehicle stopped on a hill is started, has been disclosed.
The HAC, which is a system that applies a braking force on wheels until the power from an engine increases after recognizing a hill and then removes the braking force, operates when it recognizes a predetermined level or higher of inclination in stopping of a vehicle or in braking in which a driver presses down a brake pedal.
A longitude acceleration sensor is used in the HAC to measure an inclination and the controller of the HAC determines and recognizes a hill with a predetermined level or higher inclination, using the sensed value of the longitude acceleration sensor (hereafter, abbreviated as ‘acceleration sensor’).
Basically, acceleration sensors, as shown in FIG. 1, output 0 as an acceleration value that is sensed when a vehicle runs at a constant speed on level ground and they output + and − acceleration values when a vehicle decelerates on a level ground.
Further, acceleration sensors output + and − acceleration values even when a vehicle runs at a constant speed or stops on a hill (uphill road) and a downhill road (downward slope), and they output acceleration values higher in absolute value when a vehicle accelerates on a hill or a downhill road, as compared with when it runs at a constant or stops.
A pitching motion of a vehicle is generated, as shown in FIG. 2, right after the vehicle suddenly stops, in which the output values of acceleration sensors fluctuate around the value corresponding to the actual inclination until the values are stabilized.
As described above, the actual inclination is not accurately reflected when whether a HAC operates is determined, so the HAC does not normally operate in some cases, when a vehicle starts after suddenly stopping on a hill.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.